Poles Regulate Earth Temperature, Data Suggests

Brief Summary:

1. The Earth retains heat at the equator and loses it at the poles.  The temperate zones are on the edge.  

2. The poles heat up and cool off faster than the equatorial regions  

3. Changes in earth’s radiance in the polar regions are out of proportion to the temperature change.  Temperate zones less so, but they too would participate in increased radiance and hence cooling.  

4. Increased heating from CO2 (or anything else on that scale) results in increased cooling at the poles and temperate zones that would overwhelm CO2.  

Some time ago I posted my theory that the Earth’s poles are heavily involved in the regulation of Earth’s temperature.  The Earth’s over all temperature is governed by the amount of energy being put into the system and the amount being radiated back out.  The amount being radiated back out is influenced by over all temperature, greenhouse gases that reflect radiated energy back again, and a variety of feedback loops.  Water vapor is a positive feedback loop in that a small temperature change can cause a large change in atmospheric moisture, and water vapor is a greenhouse gas.  There are also negative feedback loops, and the poles are just one of them.  

To understand this, we must have one thing firmly fixed in our mind first, which is that the poles are relatively warm.  We think of +30 C as very warm, and -40 C as very cold, but that is relative to our comfort zone and degrees C is a relative scale.  The same temperatures relative to the absolute 0 of outer space would be 303 K for very warm, and 233 K for very cold to us, but very warm compared to outer space.  With that in mind, consider the image below.  NASA has launched satellites into orbit whose job it is to measure both the incoming radiation to the planet, and what the outgoing radiation is.  This is the ERBE (Earth Radiation Budget Experiment) and while there is some debate as to how accurate it is and what the results mean, the data is more than sufficient for this discussion:  

ERBE 1985-1986. Heat is retained at Equator, Radiated at Poles

The graph at the bottom relates a specific color to the net radiation at that spot on the planet over the course of a year.  What is easy to see is that the equatorial zone retains a lot of energy.  There are 60 to 90 watts more energy per square meter going into the equatorial regions than what is coming out.  The temperate regions don’t retain nearly as much, ranging from +30 watts in some places, but less than zero for most bands and as low as -60 watts in the higher latitudes.  In brief the temperate zones likely retain less energy than they keep and so have an over all cooling effect, but it is close to being a wash.  Now consider the arctic regions.  They are losing energy to space at a rate of anywhere from -60 to -120 watts per square meter (which is why it is “cold” there!).  Greenhouse gases are thickest at the equator, and the Sun’s rays are strongest at the equator, so this makes a lot of sense.  This brings us to our first major point:  

POINT 1; The earth retains heat at the equator, and loses heat at the poles.  

Now there’s not really enough data from ERBE to establish trend lines.  If we were trying to build a model to predict the future, that would be a problem.  But all we are trying to do is prove a concept, so we don’t need data that detailed.  If we turn to the instrument record at NASA/GISS http://data.giss.nasa.gov/gistemp/tabledata/ZonAnn.Ts.txt we can see that they have provided annual mean temperatures going back to 1880 broken down by equatorial, temperate, and arctic zones.  While much of this is station data and has high error rates as a consequence, it may not be good enough for a model but it is more than we need for the purposes of this discussion.  Given that we already know the equator retains for more heat than it radiates back to space, we would expect to see the largest rises in temperatures in that zone, but we don’t.  Following is a comparison of the equatorial zone to the northern hemisphere:

Northern Hemisphere mean annual tracks with equatorial region

Given that we know that the equator retains more heat than it radiates back to space, we would expect the temperature close to the equator to go up faster than anywhere else.  Instead we see that the two trends are never more than a few tenth’s of a degree apart.  This is not big news to the climate debate.  It has been well known for a long time that northern zone temperatures are going up faster than the global average.  The reasons are well known, and not hard to understand.  Both the ocean and the atmosphere generate natural processes that move heat from the equator to the temperate zones and the poles.  The atmosphere for example, is driven by convection.  Air heats up at the equator causing it to rise.  Cooler air from the temperate zones must flow in underneath to replace it, and that pulls still cooler air from the arctic zones down into the temperate.  At the upper levels of the atmosphere, the hot equatorial air rises until it falls sideways and heads for one of the poles.  If the earth didn’t spin, this would create a giant roller, constantly moving heat to the poles and cooling the equatorial regions.  Of course the earth does spin, so this pattern gets broken up in all sorts of ways as air currents zig zag in east west directions due to daily heating and cooling from the Sun.  At the end of the day though, energy gets moved out of the equatorial regions to the poles.  The faster it is heating up at the equator, the faster the convection system would work, and we can easily see this by comparing the equatorial mean to the arctic mean:  

Poles over react to global temperature change

It is easy to see that when the equatorial region is cooler than normal, the arctic region is much cooler.  When the equatorial region is warmer than normal, the arctic is much warmer than normal.  This brings up the next important point:  

Point 2;  The poles heat up and cool off much faster than the equatorial regions.  

 We can easily spot periods where the equatorial region has varied by 1/2 degree from the long term mean while the arctic variation is two full degrees for the same time period.  What would this mean in terms of Earth’s radiance to outer space?  The formula for calculating how much energy a body will radiate at a given temperature is well known to physicists and is called Stefan’s Law:  

P (power in watts) = (constant of 5.67 x 10 to the power of -8) * (area in m2) * (temp in degrees K raised to power of 4)  

So we can actually calculate the difference in earth’s radiance for a given temperature change.  For easy figuring, let’s estimate the equatorial region mean at 300 degrees K (27 C) and the arctic mean at 230 degrees (-43 C).  The equatorial region would have a base radiance of 459.3 watts/m2 and the arctic 158.7 watts/m2.  We can now calculate the rise in radiance for a given temperature increase accounting for the temperatures at the poles rising and falling faster than the equatorial regions: 

Equatorial +0.5 K = +3.0 w/m2             Arctic + 2.0 K = +5.6 w/m2 

Equatorial +1.0 K = +6.0 w/m2             Arctic +4.0 K = +11.3 w/m2 

Equatorial +1.5 K = +9.2 w/m2              Arctic +6.0 K = +17.2 w/m2 

It may be extreme to assume a 4 to 1 variability in temperature fluctuation between arctic and equatorial, but many of the more aggressive analysis by the likes of NASA/GISS are actually suggesting eight to one. 

Point 3; Changes in Earth’s radiance in the arctic zones if far out of proportion to the change in temperature at a global level.  

That’s a pretty big negative feedback loop.  Let’s put it in the context of CO2 emissions as per the IPCC.  Their calculation is that CO2 emissions will contribute an extra 3.7 watts of energy being reflected back from the earth’s radiance, raising temperatures globally by a degree.  That’s not even enough to sustain a 1.0 degree rise at the equator since radiance there would be up 6.0 watts, let alone the extra 11.3 watts at the poles.  To accomplish that, CO2 would need an assist from water vapor.  Since water vapor is a greenhouse gas with a much larger contribution than CO2, and a small change in temperature can result in an out of proportion increase in water vapor, the theory goes that the net effect of CO2 raising temperature one degree could result in another two from water vapor for a total of 11.1 w/m2.  That’s more than enough to break even at the equator, it is a slight loss in the arctic.  By the time you get to a 1.5 degree uptick at the equator, which if you average it across the hemisphere would wind up being about the 3 degree global rise we keep hearing about, water vapor and CO2 combined, can just barely keep up with increase radiance at the equator, they are way behind in the arctic.  Add to that the fact that greenhouse effect is far lower at the poles since water vapor content is almost zero below the freezing point of water in the first place.  While I focused on the arctic zones versus equatorial to illustrate the point, let’s not forget that the temperate zones would also be part of the factor.  By assuming a temperate zone mean of about 280 K, and applying the temperature variations as reported by NASA/GISS, we can calculate the theoretical increase in radiance for both the arctic and temperate zones.  We can even add to the graph the theoretical radiance of CO2 as claimed by the IPCC:

increased earth radiance easily outstrips CO2 radiance

Point4; Increased heating from CO2 results in out of proportion increased cooling in the arctic and temperate zones 

So to review:

1. The earth retains heat at the equator and loses it at the poles

2. The poles heat up and cool off faster than the equatorial regions  

3. Changes in earth’s radiance in the polar regions are out of proportion to the temperature change.  Temperate zones less so, but they too would participate in increased radiance and hence cooling. 

4. Increased heating from CO2 (or anything else on that scale) results in increased cooling at the poles and temperate zones that would overwhelm CO2.  

Conclusion:  Earth’s radiance to space in the arctic regions has been studied far less than any of the other areas of the earth, but shows the largest variance and the least effect of greenhouse gases, while the equatorial regions where heat is clearly being retained show little variation.  This appears to be a negative feedback loop that aggressively moderates changes in earth’s over all temperature.

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11 Responses to Poles Regulate Earth Temperature, Data Suggests

  1. Tony Price says:

    You’ve misinterpreted the ERBE diagram – the diagram title is Net Radiation – from the earth. The diagram shows differences from the mean (shown as zero), so the poles are radiating about -160 wrt the mean which is 290 W/m² therefore the poles radiate about 130 W/m²). It’s what would be expected – hotter radiates more, cooler less. The hotter equatorial region and tropics radiate most, the poles least.

    The following shows the outgoing radiation rather than differences from mean – it’s April so it’s autumn in the southern hemisphere, and the south pole is radiating about 120-130 W/m².

    http://asd-www.larc.nasa.gov/erbe/ASDerbe.html

  2. davidmhoffer says:

    Thanks for making that point, but it doesn’t really change the analysis, does it? The point of the article is that because they are colder, the temperature of the poles fluctuates more in response to a change than does the equator. Yes, cold places radiate less and hot places more. But if the global temperature goes up 4 degrees on average, the distribution (numbers made up for illustration) might be +1 at the equator and +7 at the poles. The poles are still colder and radiate less than the equator, but the INCREASE is different.

  3. MostlyHarmless says:

    Yes, it does change the situation. Your first point

    “POINT 1; The earth retains heat at the equator, and loses heat at the poles”

    cannot be true, if as you agree, hotter zones radiate more than cooler ones. The diagram shows outgoing radiation – more at the equator, less at the poles, the exact opposite of that point. I’m not trying to rubbish your overall premise. I would agree that the poles radiate a higher proportion of incoming energy than equatorial zones, which is what I think you’re trying to say. After all, they spend almost 1/2 the time in darkness. and when they’re not, sunlight reaches them through a greater thickness of atmosphere, and is spread over a greater area due to low sun angle.

    I don’t argue with your second point, but I’ll have to think a bit more about your overall conclusion. CO2 may play a secondary role in controlling climate on earth, but I don’t see how climate scientists claims that mankind’s contribution (4% of 0.04%) can affect climate to produce global warming. A very tiny increase in water vapour would have the same effect, and THAT concentration is not measured accurately at present.

    • davidmhoffer says:

      I’d have to go back and look at the details, but the general idea still holds. Hotter zones radiate more heat than cold zones (true) but hotter zones GET more heat in the first place than do cold zones for exactly the reasons you state. Now consider ocean and atmospheric circulation systems which move gigantic amounts of heat from the equator to the poles. In the atmosphere for example you have a band of heating followed by cooling going around the world following the Sun. But the heating also causes convection. The largest amount of convection is at the hottest places, so air rises at the equator, pulling in cooler air from higher latitudes. At the same time the heating and cooling moving horizontaly around the planet causes a “back and forth” expansion and contraction. These create spinning areas of atmosphere called hadley cells. The net effect is to move energy from the equator to the poles, so a considerable amount of energy absorbed at the equator does wind up being radiated at the poles. If this process did not happen, the poles would be even colder and the equator even hotter.

      I agree that CO2 doesn’t do what alarmists claim, but your explanation is missing some pieces. The way the climate scientists get around your logic is this. Water vapour at ocean surface at 15 degrees C runs in the 30,000 to 40,000 ppm range. Even though CO2 is a more efficient absorber at the specific spectrum in question, at 380 ppm it has no appreciable effect on the total. But when one starts moving upward in altitude, temperatures get colder, and the amount of water vapour that exists drops off. The higher you go the lower the temperature the less water vapour and at some point (I forget, -12 or something) the CO2 is still at about 380 ppm and is significant compared to the amount of water vapour. So its not the average concentration that they use to make their argument, but the distribution of the concentrations. From their you have to start considering still more factors like change in emission spectrum due to colder temperatures at high altitude, presense of clouds, changes to convection and hadley cell patters, reduction of reabsorption due to increased water vapour blocking downward photon re-radiated by CO2 as well as upward photons re-radiated from surface and on and on and on…

  4. davidmhoffer says:

    I just checked and I had it right the first time. If you take a look at http://eos.atmos.washington.edu/erbe/
    They have incoming, outgoing, and net. The incoming at the equator is a lot higher than the outgoing and the difference is the net. So in the net pic, the positive values are w/m2 being absorbed and the negative values are w/m2 being lost to space.

  5. Excellent!
    Thanks, David.

    I have linked to your blog from my climate and meteorology pages (English and Spanish).

  6. mukesh says:

    why there is so much heat in india? Can there some temperature will get decrease ever? Plz rply

    • davidmhoffer says:

      Ever is a very long time 🙂
      India is very warm because it is cose to the equator where the sun’s rays are the strongest. It is also half surrounded by ocean that has warm currents that release heat into the atmosphere that wind then blows over the land. Also, much of India is “low altitude” meaning that it isn’t very far above sea level. Heat tends to “collect” in low lying areas while in high altitudes (such as the tops of mountains in the Himalayas) it tends to radiate away making the high elevations cold.

      So, while I would expect that India might see some minor variation in temperature from year to year and decade to decade, it will remain a very warm country for centuries or more.

  7. Jeremy says:

    We absolutely love your blog and find almost all of your post’s to
    be exactly I’m looking for. can you offer guest writers to
    write content in your case? I wouldn’t mind composing a post or elaborating on a lot of the subjects you write concerning here.
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    • davidmhoffer says:

      I’m not really actively running this blog anymore, I just leave it up because people link to various articles. Thanks for the kudos though. I’m still writing the odd article hear and there, but I publish on WUWT http://wattsupwiththat.com/ where you will find a lot more content in a lot more detail from authors far more qualified than I.

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